1. Field of the Invention
The present invention relates to a soft magnetic film for use in a magnetic head or core material of a magnetic recording and reproducing apparatus such as a video cassette recorder (VCR), an audio recording and reproducing apparatus and a magnetic recording apparatus for a computer.
2. Description of the Prior Art
In response to the requirement of the high recording density in a recent magnetic recording technology, much attention has been paid to the development of a magnetic head having a superior performance.
In order to satisfy the requirement mentioned above, various types of magnetic heads have been developed: One example as shown in FIG. 10 is a magnetic head of a laminated-type head having a ring shape in which the core material is made of an integrated layers of a soft magnetic film 17 and an electric insulating film 18 integrated alternately to each other and is sandwitched between a pair of non-magnetic substrates 19. The core material forms a magnetic path. 20 denotes a glass material and 21 a magnetic gap.
Another example as shown in FIG. 12 is a magnetic head (referred to as MIG head) in which the majority of the magnetic path is composed of ferrite material 22 and at the vicinity of the magnetic gap 23 easily saturated magnetically there is provided with a soft magnetic film 24. 25 denotes a glass material.
In the case of the laminated type head, there is shown a contacting surface in FIG. 11, while in the case of MIG type head there is shown a contacting surface in FIG. 13.
In the magnetic heads, the performance thereof relates closely to the material characteristics of the core material. In order to achieve a high recording density, it is necessary for the core material to have a high saturation magnetic flux density (related to mainly to the recording characteristics) and a high magnetic permeability (related mainly to the reproducing characteristics).
In spike of the above requirements, the soft magnetic film made of a conventional Permalloy, Sendust, Co-based amorphous alloy can achieve a high saturation magnetic flux density as low as 1T more or less and can not realize the high density recording because of their limited high saturation magnetic flux density.
Therefore, much attention has been paid to the development of the soft magnetic film made of microcrystals. One of researches is related to a Fe--M--N type film wherein M is an atom or atoms selected from the group consisting of Zr, Hf, Ti, Nb, V, Mo and W as reported in Japanese Patent Kokai No. 2-275605. The other is related to a Fe--M--B--N type film wherein M is an atom or atoms selected from the group consisting of Ta, Zr, Hf, Nb and Ti as reported in Japanese Patent Kokai No. 4-367205.
It is reported in Japanese Applied Magnetic Institute Paper Vol. 14, No. 3 that, the soft magnetic film made of microcrystals provides a large loss of the magnetic permeability at a high frequency band in comparison with the Co-based amorphous alloy film although it has a high saturation magnetic density. In order to improve a rate of reproduction by means of the magnetic head at the high frequency band, it is necessary to improve the magnetic permeability at the high frequency band.
It is generally known in the case of the film made of Sendust and Co-based amorphous alloy that, a thinner thickness of the magnetic film makes the magnetic permeability at the high frequency band improved and also known that, broad band of the magnetic permeability can be realized due to a decrease of an eddy current loss by using a multilayer sot magnetic film prepared by alternatively laminating magnetic layers having a same thickness (3-8 .mu.m) and electric insulating
Contrary to this, however, in the case of the soft magnetic multilayer film prepared by alternative lamination of said microcrystal soft magnetic layers and non-magnetic insulating layers, it is found that, thinner and uniform soft magnetic layers and thick non-magnetic insulating layers make the total thickness of the magnetic layers to be decreased and thus the magnetic saturation flux density to be decreased, resulting in degradation of the recording characteristic of the laminated type magnetic head due to incomplete feature utilization of the microcrystal soft magnetic film. Further, the microcrystal film becomes difficult to obtain such an isotropic high magnetic permeability accompanied with an decrease of the film thickness, resulting in degradation of the reproduction characteristic of the laminated type magnetic head.
Furthermore, in the case of using the microcrystal soft magnetic film as a core material of the MIG head or the main pole excitation system head, the soft magnetic film is formed in an strip shape of about 10 .mu.m wide, resulting in decrease of the magnetic permeability due to generation of reflux magnetic domains.